Most Helpful Girl
You can't. They need to seek professional help from a reputable therapist, who will work with them to help change their mindset , and get to the root cause of their depression.
The best thing you can do is encourage and support them through their therapy. Suicidal people suffer from relentless , immeasurable emotional pain , and they rarely reveal their innermost thoughts to anyone, and they never tell anyone how they are really feeling.
Suicidal people have many underlying unresolved issues. My heart goes out to anyone who contemplates taking their own life, because they don't really want to end their life, they want to put an end to their emotional pain and suffering .
Most Helpful Guy
Just remind them constantly that it would really, really hurt you if they were gone. Most people don't think it will hurt anyone if they aren't around anymore. They think it will actually make everyone happier.
Keep drilling into them that you need them around and keep letting them know that their problems are not stupid and they shouldn't feel embarrassed about them and that you're willing to listen any time they need to talk. All the while continue asking them to consider professional help because you want them to get better, and tell them that that is not a sign of weakness or anything to be embarrassed about.